Electric Vehicle Charging Station Dynamically Responding to Power Limit Messages Based on a Recent History of Power Provided

ABSTRACT

An electric vehicle charging station charging electric vehicles dynamically responds to power limit messages. The charging station includes a charging port that is configured to electrically connect to an electric vehicle to provide power to charge that electric vehicle. The charging station also includes a power control unit coupled with the charging port, the power control unit configured to control an amount of power provided through the charging port. The charging station also includes a set of one or more charging station control modules that are configured to, in response to receipt of a message that indicates a request to limit an amount of power to an identified percentage and based on a history of power provided through the charging port over a period of time, cause the power control unit to limit the power provided through the charging port to the identified percentage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/611,540, filed Mar. 15, 2012, which is hereby incorporated byreference

FIELD

Embodiments of the invention relate to the field of electric vehiclecharging; and more specifically, to an electric vehicle charging stationdynamically responding to power limit messages based on a recent historyof power provided.

BACKGROUND

Demand response is a common way to manage power consumption in responseto supply conditions. For example, customers may register as demandresponse customers with their local power utility to receive a reducedrate for their energy usage while allowing the power utility to reducetheir load during periods of high demand.

Electric vehicle supply equipment (EVSE), commonly referred to aselectric vehicle charging stations, are used to charge electric vehicles(e.g., electric battery powered vehicles, gasoline/electric batterypowered vehicle hybrids, etc.). Some electric vehicle charging stationsmay include the ability to respond to demand response load controlmessage to reduce load by turning off the charging station or a chargingstation port.

SUMMARY

An electric vehicle charging station charging electric vehiclesdynamically responds to power limit messages. The charging stationincludes a charging port that is configured to electrically connect toan electric vehicle to provide power to charge that electric vehicle.The charging station also includes a power control unit coupled with thecharging port, the power control unit configured to control an amount ofpower provided through the charging port. The charging station alsoincludes a set of one or more charging station control modules that areconfigured to, in response to receipt of a message that indicates arequest to limit an amount of power to an identified percentage andbased on a history of power provided through the charging port over aperiod of time, cause the power control unit to limit the power providedthrough the charging port to the identified percentage.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention. In the drawings:

FIG. 1 illustrates an exemplary system for dynamically responding topower limit messages based on a recent history of power provided throughthe charging station according to one embodiment;

FIG. 2 is a flow diagram illustrating exemplary operations for anelectric vehicle charging station dynamically responding to power limitmessages based on a recent history of power provided through thecharging station according to one embodiment;

FIG. 3 is a flow diagram illustrating exemplary operations for samplingpower according to one embodiment;

FIG. 4 illustrates an example where there are multiple demand responseload control messages being received during the same demand responseevent (without the demand response event being cleared) and the chargingstation interprets them independently and separately according to oneembodiment;

FIG. 5 illustrates an example where there are multiple demand responseload control messages being received during the same demand responseevent (without the demand response event being cleared) and the chargingstation interpreting them progressively according to one embodiment; and

FIG. 6 illustrates an exemplary embodiment of a charging stationaccording to one embodiment of the invention.

DESCRIPTION OF EMBODIMENTS

In the following description, numerous specific details are set forth.However, it is understood that embodiments of the invention may bepracticed without these specific details. In other instances, well-knowncircuits, structures and techniques have not been shown in detail inorder not to obscure the understanding of this description. Those ofordinary skill in the art, with the included descriptions, will be ableto implement appropriate functionality without undue experimentation.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. In the following description and claims, the term “coupled”along with its derivatives, may be used. “Coupled” is used to indicatethat two or more elements, which may or may not be in direct physical orelectrical contact with each other, co-operate or interact with eachother.

A method and apparatus for an electric vehicle charging station(“charging station”) dynamically responding to power limit messagesbased on a recent history of power provided through the charging stationis described. In one embodiment, responsive to receiving a message thatindicates a request to limit the amount of power to an identifiedpercentage, the charging station limits the amount of power providedthrough a charging port to at least the identified percentage based on arecent history of power provided through that charging port over adefined period of time. In one embodiment, the message is sent as partof a demand response event, and is a demand response load controlmessage.

In one embodiment, the charging station or another device that iscapable of monitoring the amount of power being drawn through thecharging station, periodically samples the power being dispensed throughthe charging port(s) of the charging station (e.g., a sample every 60seconds), and stores a predefined number of the latest samples (e.g., abuffer of ten samples). By way of a specific example, storage isallocated for a predefined number of samples (e.g., 10). Once thatnumber of samples has been taken, the next sample pushes the oldestsample out. Each sample may also include the time elapsed between thatsample and the previous sample, as the time between samples may vary(referred herein as the duration). Responsive to a power limit messagebeing received that indicates a request to limit the power beingdispensed to a certain percentage, the charging station (or anotherdevice that is sampling the power) determines the amount of power thatwill subsequently be allowed to be drawn through one or more of itscharging ports(s) based on the most recent samples (e.g., the samples inthe buffer) and the requested percentage. The charging station thencauses the amount of power that is capable of being drawn to be setaccording to the determined value.

In one embodiment, if the determined value is below a threshold (e.g.,less than 6 amps), then no amount of power will be allowed to be drawnthrough the charging station during a power limiting event. As anexample, if the power samples indicate that there has not been powerrecently drawn through the charging station (e.g., the charging stationis idle), then no power will be dispensed through the charging stationduring the power limiting event.

In one embodiment, the recent history of power provided through thecharging station is based on the average of the stored power samples. Inanother embodiment, the recent history of power provided through thecharging station is based on the maximum of the stored power samples. Inanother embodiment, the value of the recent history of power providedthrough the charging station is calculated as the sum of the product ofthe current samples and their duration, divided by the total sampleduration.

FIG. 1 illustrates an exemplary system for dynamically responding topower limit messages based on a recent history of power provided throughthe charging station according to one embodiment. The charging station120 is used to charge electric vehicles (e.g., electric battery poweredvehicles, gasoline/electric battery powered vehicle hybrids, etc.). Thecharging station 120 may be located in a designated charging location(e.g., similar to a gas station), near parking spaces (e.g., publicparking spaces and/or private parking spaces), private residences, etc.The charging station 120 may be controlled (e.g., owned or leased) bygovernments, businesses, utilities, organizations, residentialcustomers, or other entities. As illustrated in FIG. 1, the chargingstation 120 supplies power through the power line 135 via the power grid130, which is operated by the utility 135. Although FIG. 1 illustrates apower grid operating a utility supplying power to the charging station,embodiments are not so limited as different power sources may besupplying power to the charging station (e.g., a solar array). In someembodiments, which will be described in greater detail later herein, theutility 135 issues demand response load control messages during demandresponse events.

The charging station 120 includes one or more charging ports 155, eachof which may provide a connection point to an electric vehicle forcharging. For example, the charging port(s) 155 may include connectionsand circuitry for attached charging cords (e.g., with a connectorconforming to SAE Electric Vehicle and Plug in Hybrid Electric VehicleConductive Charge Coupler, J1772 Proposed Draft, November 2009 (“SAEJ1772”)) for charging electric vehicles. The charging port(s) 155 mayinclude standard power receptacles (e.g., conforming to NEMA (NationalElectrical Manufacturers Association) standards 5-15, 5-20, 14-50 orother standards (e.g., BS 1363, CEE7, etc.) and may operate at differentvoltages (e.g., 120V, 240V, 230V, etc.)). The charging port(s) 155 maybe capable of supporting DC charging. The charging port(s) 155 mayinclude circuitry for inductively charging electric vehicles.

The charging station 120 is coupled with the charging station networkserver 125 (hereinafter “server”). The charging station 120 may becoupled with the server 140 over a Wide Area Network (WAN) such as theInternet, over a Local Area Network (LAN), and/or through a chargingstation gateway and/or payment station (not illustrated) that may relaycommunication between the charging station 120 and the server 125. Thecharging station gateway may in itself provide charging service. Theserver 125 may be owned and administered by a network operator (notillustrated) and may be a different entity than who owns or controls thecharging station 120. As will be described in greater detail laterherein, the server 125 may issue power limit messages (such as demandresponse load control messages) to the charging station 120.

The charging station 120 may periodically send the amount of power beingconsumed by an electric vehicle to the server 125. This data may be usedby the utility or other entity when determining how much to shed fromthe load.

Although FIG. 1 illustrates a single charging station coupled with theserver 125, it should be understood that typically multiple chargingstations are coupled with the server 125 and communicate with the server125. For example, the server 125 may maintain station identificationinformation and communication information such that it can transmitmessages to each of the charging stations. The server 125 may alsoinclude information on established charging sessions such as electricvehicle operator identification information, and electric vehicleoperator preferences. As will be described in greater detail laterherein, in some embodiments, electric vehicle operators may opt-out ofthe demand response service such that demand response events will notaffect their charging (typically for a higher rate).

Operators of electric vehicles may be required to be authorized in orderto use a particular charging station and/or charging port. In oneembodiment, operators request charging sessions, where each requestincludes an access identifier. In one embodiment, the access identifieris included in an RFID enabled device that is assigned to an electricvehicle operator. The operator may swipe/wave the RFID enabled devicenear an RFID reader of the charging station (or a gateway and/or paymentstation coupled with charging station) to present the access identifierand request the charging session. In another embodiment, operatorsrequest charging sessions and provide an access identifier (e.g.,username/password, email address, phone number, PIN, account number,etc.) in which the operator may enter into a user interface provided onthe charging station, payment station coupled with the charging station,and/or through a web interface (e.g., on a mobile app). In oneembodiment, the charging station (or a gateway or payment stationcoupled with the charging station) transmits the request to the server125 for authorization. The authorization request transmitted to theserver 125 includes the access identifier and may also include anidentifier of the charging station that uniquely identifies the chargingstation. In another embodiment, the authorization is performed locallyon the charging station 120.

The charging station 120 includes a power control unit 150 that controlsthe amount of power that can be drawn by an electric vehicle through oneof the charging port(s) 155. In some embodiments, the power control unit150 is a solid state device or any other device suitable for controllingthe flow of electricity that can energize or de-energize a charging portand/or variably control the amount of current that can be drawn througha charging port. The power control unit 150 may also be used to signalthe maximum available current capacity through a charging port to anelectric vehicle (e.g., through Pulse Width Modulation (PWM) circuitry).In some embodiments, the power control unit 150 is controlled byinstructions from the charging station control modules 140. For example,as will be described in greater detail later herein, in response toreceiving a power limit message to limit the amount of powerconsumption, the charging station control modules 140 may instruct thepower control unit 150 to modify the amount of current that can be drawnthrough a charging port based on the recent history of power providedthrough that charging port. In some embodiments there is a separatepower control unit 150 for each of the charging port(s) 155.

The charging station 120 may also include the power sampling unit 145that samples the power being dispensed through a charging port. Thepower sampling unit 145 may be a meter or any other device that canmeasure current or power. The power sampling unit 145 may periodicallytake power samples, each power sample indicating an amount of powerpresently being dispensed through the sampled charging port. By way ofexample, the power sampling unit 145 may sample every 60 seconds (orother defined time, which may be configurable) each having a duration of1 second (or other defined time, which may be configurable).

The power sampling unit 145 may take samples according to instructionsfrom the charging station control modules 140 according to oneembodiment. In one embodiment, samples are only taken while charging isongoing (that is, an electric vehicle is connected to the chargingstation) and there is not a power limiting event such as a demandresponse event. The charging station control modules 140 cause the powersamples to be stored in the power samples storage 160, which in someembodiments is non-volatile memory. In one embodiment, a sliding windowof power samples is buffered in the power samples storage for an ongoingcharging session (e.g., the last ten power samples of an ongoingcharging session). When a charging session ends and there is not a powerlimiting event, the buffered power samples for that charging session maybe removed.

While FIG. 1 illustrates that the power sampling unit 145 and powersamples 160 are part of the charging station 120, embodiments are not solimited. For example, power samples may be taken by devices external tothe charging station 120 that are capable of measuring the powerdispensed by the charging station 120 to the electric vehicle 110, andstored/buffered in those devices. As another example, the chargingstation 120 may transmit the power samples to an external entity (e.g.,the server 125, a gateway unit, etc.) that may use them to calculate therecent history of power provided.

As illustrated in FIG. 1, at an operation 1, the electric vehicle 110 ischarging through one of the charging port(s) 155 and drawing a firstamount of current (first amp amount). In this example, the electricvehicle 110 is initially being charged while not being subject to apower limiting event such as a demand response event.

At an operation 2, the charging station control modules 140 cause thepower sampling unit 145 to periodically sample the power that is beingdispensed to the electric vehicle 110 (e.g., a sample of 60 seconds),and store the samples in the power samples 160 (e.g., a buffer of mostrecent samples). The charging station control modules 140 may transmitthe power samples to an external entity (e.g., the server 125, a gatewayunit, etc.).

Sometime later, at an operation 3, the charging station 120 receives amessage that indicates it should limit power consumption to a certainpercentage (e.g., reduce to X%). The message may be sent from theutility 135, the charging station network server 125, or from anotherentity.

By way of a specific example, the charging station network server 125includes a demand response module 170 that allows a utility, a chargingstation owner, or other entity to cause a demand response load controlmessage to be sent to the charging station 120 as well as potentiallyother charging stations that are to be affected by a demand responseevent. For example, due to strain on the power grid 130, an employee atthe utility 135 may determine to reduce the load of the chargingstations on the power grid 130 (including the charging station 120) to acertain percentage (e.g., reduce the load to 75%). The utility employeemay use the demand response module 170 to cause a message to be sent tothe charging stations on the power grid 130 to reduce their load to atleast 75%. The demand response module 170 may also be used to selectcertain charging stations (e.g., a portion of the stations on the powergrid 130) in which to effect a demand response event. In one embodiment,the demand response module 170 allows the configuration of demandresponse triggers to automatically respond to demand response events,which may or may not take as input other non-charging station load onthe power grid.

In some embodiments, operators of electric vehicles may opt-out of beingaffected by demand response events or other power limiting events. Insuch an embodiment, prior to transmitting a power limit message to acharging station to be applied to a charging port, the server 125determines whether there is an active charging session on that chargingport. If there is, the server 125 then determines whether the powerlimit event is applicable to the operator associated with that chargingsession. This may be determined, for example, based on the accessidentifier that may be presented when requesting the charging session.If the power limiting event is not applicable to the operator, then apower limit message will not be sent for that port (at least until thatcharging session has terminated). If the power limit event isapplicable, then a power limit message may be sent for that port. Inaddition, if a charging station has already limited the power that canbe drawn through a charging port due to a power limit event when anoperator requests a charging session, the server 125 may determinewhether that operator has opted-out of that event. For example, theoperator may opt-out of demand response events. If so, then the server125 may send a message to the charging station to remove the limit onthe power for that port, at least until that charging session isterminated.

At operation 4, the charging station 120 limits the power that it willprovide to at least not exceed the requested percentage of the recenthistory of power provided. In one embodiment, the charging stationcontrol modules 140 calculate the recent history of power providedthough the charging port 155 connecting the electric vehicle 110 and thecharging station 110 based on the power samples 160 stored for thatcharging session. The calculation may be based on the average of thestored power samples 160. For example, the value of the recent historyof power provided may be calculated as the sum of the product of thesamples and their duration, divided by the total sample duration.Alternatively, the calculation may be based on the maximum of the storedpower samples 160. In an alternative embodiment, an entity external tothe charging station 120 computes the recent history of power provided.For example, the server 125, a gateway unit, or any other applicationthat can access the power samples (whether the power samples are storedon the charging station 120 and/or a different device), may calculatethe recent history of power provided. The external entity may transmitto the charging station 120 the calculated recent history of powerprovided.

Based on the recent history of power provided, the charging stationcontrol modules 140 limit the power provided through the charging portaccording to the requested percentage received in operation 3. By way ofexample, if the recent history of power provided through the chargingport 155 is 16 amps and the message indicates to limit the load to 75%,the charging station control modules 140 cause the energy control unit150 to limit the power provided through the charging port 155 to 12amps.

In one embodiment, the energy control unit 150 signals the electricvehicle 110 (e.g., through PWM circuitry) its modified current capacitythrough the charging port 155 (e.g., 12 amps in the example above). Ifthe electric vehicle 110 does not respect the signaling (e.g., does notlimit its power consumption to the signaled amount), the chargingstation 120 may terminate the charging session and prevent furthercharging from the vehicle 110 (at least during the power limit event oruntil a future modification raises the limit sufficiently). In anotherembodiment, the energy control unit 150 imposes the voltage and currentthat can be delivered to the electric vehicle 110 through the chargingport 155.

Some charging implementations, such as those implementing SAE J1772,have a minimum power value for charging. For example, implementationsconforming to SAE J1772 do not charge under 6 amps. In some embodiments,if the limit is determined to be lower than the minimum value, then thecharging station control modules 140 cause the energy control unit 150to de-energize the charging port 155 thereby preventing power from beingdelivered.

After the energy control unit 150 causes the power provided to belimited, at operation 5, the electric vehicle 110 is limited to drawingpower according to that limit (of course, the electric vehicle 110 maydraw power below that limit) The charging station 120 may, at operation6, transmit an acknowledgement to the server 125 (or the other entitythat sent the message in operation 3) that indicates that the powerprovided has been limited as requested. In one embodiment, if the server125 (or the other entity that sent the message) does not receive anacknowledgment, then other charging stations whose power provided waslimited may need to be limited further in order to reduce the load bythe desired amount.

It should be understood that the electric vehicle 110 will be limited todrawing power according to the modification until the power limitingevent is finished. In one embodiment, other electric vehicles that usethe same port after the electric vehicle 110 will also be subject to themodified power limit while the power limiting event exists.

A power limiting event, such as a demand response event, may terminatein a number of ways. For example, the power limiting event may exist fora defined period of time (e.g., one hour), the expiration of whichcauses the power limit to be automatically removed. As another example,the charging station 120 may receive a message from the server 125 thatindicates that the power limiting event has terminated, and respond bycausing the power limit to be removed.

FIG. 2 is a flow diagram illustrating exemplary operations for anelectric vehicle charging station dynamically responding to power limitmessages based on a recent history of power provided through thecharging station according to one embodiment.

At operation 210, the charging station receives a message that indicatesa request to limit an amount of power to an identified percentage. Themessage may be sent as a result of a demand response event, and may be ademand response load control message. The message may be applicable toone or more charging ports of the charging station. However, for thepurposes of FIG. 2, a single charging port will be described. Themessage may be sent by a utility controlling the power grid servicingthe charging station, a charging station network server, or from anotherdevice such as a demand response automation server (DRAS). A DRAStypically receives a demand response signal from utility software, andforwards that message to participating entities, which may includecharging stations, or an aggregator such as the charging station networkserver.

Flow moves from operation 210 to operation 215, where the chargingstation, based on a history of power provided through the charging portover a period of time, causes the amount of power that is capable ofbeing provided through the charging port to be limited according to theidentified percentage.

By way of example, the average amperage over the period of time iscalculated and that average is used when limiting to at least therequested percentage. As a specific example, if the average amperageover the period of time is 32 amps and the message indicates to limitthe load to 25%, then the charging station causes the amps that can bedrawn through the charging port to be limited to not exceed 8 amps. Ofcourse the average amperage is an example, and other mechanisms may beused to calculate the history of power provided.

As another specific example, if there is not a recent history of powerprovided through the charging port at the time the message is received(e.g., there are no power samples because that port was idle), thenregardless of the specific percentage requested, the charging stationcauses no power to be drawn through the charging port (at least untilthe power limit event terminates).

In another embodiment, an entity external to the charging station (e.g.,a gateway device, the charging station network server, etc.) calculatesthe recent history of power provided through the charging port, andcommunicates this information to the charging station.

Flow then moves to operation 220, where the charging station mayoptionally transmit an acknowledgement to the entity that sent themessage in operation 210, the acknowledgement indicating that the powerlimiting was successful. For example, the acknowledgement may indicatethe power limit that was set (e.g., the power has been reduced to 12amps in this example). The charging station may continue to transmitmessages to the server 125 on a regular basis that contain measures ofthe power presently being delivered and the accumulated energy that hasbeen delivered to date during a charging session. This information maybe used to verify that the power limiting action has successfully takenplace.

FIG. 3 is a flow diagram illustrating exemplary operations for samplingpower according to one embodiment. At operation 310, a charging sessionis established between an electric vehicle and a charging station andcharging commences. Flow then moves to operation 315, and the chargingstation periodically samples and buffers the amount of power beingconsumed by the electric vehicle through the charging station. By way ofa specific example, storage is allocated for a predefined number ofsamples (e.g., 10). Once that number of samples has been taken, the nextsample pushes the oldest sample out. Each sample may also include thetime elapsed between that sample and the previous sample, as the timebetween samples may vary (referred herein as the duration).

Flow then moves to operation 320, where responsive to the chargingsession terminating and charging ceasing, the charging station clearsthe buffer of power samples. Although not illustrated in FIG. 3, if apower limit message such as a demand response load control message isreceived at the charging station prior to the charging sessionterminating, the charging station will not remove the buffer of powersamples that exist at the time the message is received, in oneembodiment, as these will be used when calculating the recent history ofpower provided.

Multiple Power Limit Messages

In some situations, multiple power limit messages may be received at acharging station during a power limiting event. For example, a firstmessage requesting a reduction to 50%, followed by a second messagerequesting a reduction to 75%. The following examples provided in FIGS.4 and 5 describe a demand response event, but may be applicable to othertypes of power limiting events.

In one embodiment, the charging station interprets multiple demandresponse load control messages (that are part of the same demandresponse event) independently and separately, and modifies the powerlimit based on the power samples existing when the first one of themultiple demand response load control message is received. In thisembodiment, power samples are taken only when a demand response eventdoes not exist (samples are not taken when a demand response eventexists).

FIG. 4 illustrates an example where there are multiple demand responseload control messages being received during the same demand responseevent (without the demand response event being cleared) and the chargingstation interprets them independently and separately. At operation 410,charging commences between the electric vehicle 402 and the chargingstation 120, which is drawing power from the power grid 130 through thecharging station 120. The charging station 120 samples the powerpresently being consumed by the vehicle 402 at operation 415, which forpurposes of this example is 16 amps. The power samples may be stored inthe power sample storage 160. Sometime later, at operation 420, thecharging station 120 receives a message to limit the power to 50%, sentby the server 125 (of course, the message may be sent by another entityas previously described). The message indicates the start of the demandresponse event 428. The charging station then causes the power that canbe drawn to be limited to 8 amps. Sometime later, at operation 425,charging terminates (e.g., the operator disconnects the vehicle 402 fromthe charging station 120). It should be understood that in this example,the power samples that existed at the time the power limit message isreceived, which indicate a power of 16 amps, are not removed while thedemand response event exists.

Sometime later, at operation 430, charging commences between theelectric vehicle 404 and the charging station 120. It should be notedthat the power samples are not taken at this time since the chargingstation 120 is in a demand response event. Also, since the chargingstation 120 is still in a demand response event, the electric vehicle404 is limited to charging at 8 amps. Sometime later, at operation 435,the charging station 120 receives a message to limit the power itdelivers to 75%. In this embodiment, the charging station 120 modifiesthe power limit based on the power samples existing when the firstdemand response load control message is received. Thus, the chargingstation 120 uses the power samples collected in operation 415 (whichindicate 16 amps) when modifying its power limit As a result, thecharging station 120 causes the power that can be drawn to be limited to12 amps.

Sometime later, at operation 440 the charging station 120 receives amessage that clears the demand response event 420. For example, themessage may be a demand response load control message indicating thecharging station 120 can supply 100% of its rating (it is not limited).This represents the end of the demand response event 428. Since thedemand response event 428 has ended, the charging station 120 clears thepower samples it has taken (which indicated 16 amps) at operation 445,and begins to take new power samples at operation 450, which in thisexample indicate the vehicle 404 is charging at 30 amps.

In another embodiment, the charging station interprets multiple demandresponse load control messages progressively (dependent on the previousmessage). In this embodiment, power samples are taken both when a demandresponse event does not exist and when a demand response event exists.

FIG. 5 illustrates an example where there are multiple demand responseload control messages being received during the same demand responseevent (without the demand response event being cleared) and the chargingstation interpreting them progressively. At operation 510, chargingcommences between the electric vehicle 502 and the charging station 120.The charging station 120 samples the power presently being consumed bythe vehicle 502 at operation 515, which for this example is 16 amps (thesame as in FIG. 4). The power samples may be stored in the power samplestorage 160. Sometime later, at operation 520, the charging station 120receives a message to limit the power to 50%, sent by the server 125 (ofcourse, the message may be sent by another entity as previouslydescribed). The message indicates the start of the demand response event528. The charging station then causes the power that can be drawn to belimited to 8 amps. Sometime later, at operation 525, charging terminates(e.g., the operator disconnects the vehicle 502 from the chargingstation 120).

Sometime later, at operation 530, charging commences between theelectric vehicle 504 and the charging station 120. It should be notedthat, unlike the example illustrated in FIG. 4, power samples are takenduring a demand response event in this embodiment. Thus, at operation532, the charging station samples the power presently being consumed bythe vehicle 504. However, since the charging station has already limitedits power to 8 amps, the samples will not exceed 8 amps. In thisexample, the power samples that are taken indicate that the vehicle 504is charging at 8 amps. Sometime later, at operation 535, the chargingstation 120 receives a message to limit the power to 75%. In thisembodiment, the charging station 120 modifies the power limit based onthe latest power samples, which in this case 8 amps. As a result, thecharging station 120 causes the power that can be drawn to be limited to6 amps.

Sometime later, at operation 540 the charging station 120 receives amessage that clears the demand response event 520. For example, themessage may be a demand response load control message indicating thecharging station 120 can supply 100% of its rating (it is not limited).This represents the end of the demand response event 528. The chargingstation then removes its power limit and continues to take power samplesat operation 550, which indicate the vehicle 504 is charging at 30 amps.

As described above, some electric vehicle charging stations may includemultiple charging ports (referred herein as a “multi-port chargingstation”). In some embodiments that are described above, the chargingstation treats each charging port independently. That is, the limit ofpower provided through each charging port is independently determinedbased on the recent history of power provided for that individualcharging port (not taking into consideration the recent history of powerprovided through other charging ports).

In other embodiments, a multi-port charging station treats multiple onesof its charging ports as a group, and the limit of power providedthrough a particular charging port is based, at least in part, on therecent history of power provided through the aggregate of the group ofcharging ports. In these embodiments, responsive to receiving a messagethat indicates a request to limit the amount of power to an identifiedpercentage and based on the recent history of power provided through theaggregate of the group of charging ports, the multi-port chargingstation may manage a budget of power that it can supply and allocate tothose charging ports, while not exceeding the identified percentage. Byway of example, if a charging station includes two charging ports, eachof which is presently supplying 15 amps (for an aggregate total of 30amps) and a message is received to limit to 50%, the charging stationmay manage the allocation of the 15 amps between those ports.

As one example, the power allocation may be “fair” where each chargingport receives the same allocation (in this example 7.5 amps). As anotherexample, the power allocation may be based on a policy based on one ormore factors such as operator preferences (e.g., whether the operator ispart of a preferred program), the state of charge of the vehiclesconnected to the ports (e.g., ports with vehicles that are relativelymore charged or fully charged may receive an allocation less than portswith vehicles that are relatively less charged or not fully charged),the type of electric vehicles connected to the ports (e.g., ports thatare connected to fully electric battery powered vehicles may beallocated more power than ports that are connected to gasoline/electricbattery powered hybrid vehicles), the duration of the charging sessions(e.g., ports with vehicles that have been charging for a relativelylonger period of time may be allocated less power than ports withvehicles that have been charging for a shorter period of time), theamount of power that has been delivered to the vehicles (e.g., portswith vehicles that have been supplied relatively larger amounts of powermay be allocated less power than ports with vehicles that have beensupplied a smaller amount of power), etc.

The power allocation may be dynamic and change. For example, if acharging session ends (e.g., a vehicle operator disconnects the vehiclefrom the charging station), the charging station may re-allocate thepower across the charging ports.

Charging stations may be part of the same logical group and/or radiogroup. A radio group is a collection of one or more charging stationsthat collectively have a single connection to the charging stationnetwork server, which is provided through a gateway unit, which may beincluded in one of the charging stations in that radio group. Thegateway unit, or other controller, may manage the charging stationmembers of the radio group. A logical group is a collection of one ormore charging stations that may or may not be part of the same radiogroup, and may be geographically distributed. The charging stations thatare members of a logical group are often configured by a systemadministrator or the owner of those charging stations. In oneembodiment, the charging station network server allows administrators,owners, or other authorized entities to define logical groups includingits members. The server, or another device that is coupled with thestations, may manage the members of the logical groups.

In some embodiments, the power limiting is provided at a chargingstation group level (e.g., a radio group, a logical group). For example,the limit of power provided through a charging station or charging portmay be based, at least in part, on the recent history of power providedthrough the aggregate of the charging stations or charging ports. Forexample, the charging stations may periodically transmit the powersamples to the charging station network server, which maintains and canaggregate the values for calculating the recent history of powerprovided through a group of charging stations. In these embodiments, thecontroller of a group (e.g., a gateway unit, the server) may receive arequest to limit the amount of power to an identified percentage, andbased on the recent history of power provided through the aggregate ofthe group, and allocate power across the members of the group, while notexceeding the identified percentage. For example, after determining theallocations of power, the controller (e.g., the server, the gatewayunit) may transmit messages to the charging stations in the group toapply the allocations.

Similarly as in the multi-port charging stations, there are differentways to determine how to allocate the power. For example, the powerallocation may be “fair” where each member of the group receives thesame allocation. As another example, the power allocation may be basedon a policy based on one or more factors such as operator preferences,the state of charge of the vehicles connected to the ports, the type ofelectric vehicles connected to the ports, the duration of the chargingsessions, the amount of power that has been delivered to the vehicles,etc.

FIG. 6 illustrates an exemplary embodiment of a charging stationaccording to one embodiment of the invention. It should be understoodthat FIG. 6 illustrates an exemplary architecture of a charging station,and other, different architectures may be used in embodiments of theinvention described herein. For example, one or more of the componentsillustrated in FIG. 6 may not be included in some embodiments.

As illustrated in FIG. 6, the charging station 600 includes the energymeter 610, the power control unit 615, the charging port 620, thevolatile memory 625, the non-volatile memory 630 (e.g., hard drive,flash, PCM, etc.), one or more transceiver(s) 635 (e.g., wiredtransceiver(s) such as Ethernet, power line communication (PLC), etc.,and/or wireless transceiver(s) such as 802.15.4 transceivers (e.g.,ZigBee, etc.), Bluetooth, WiFi, Infrared, GPRS/GSM, CDMA, etc.), theRFID reader 640, the display unit 645, the user interface 650, and theprocessing system 655 (e.g., one or more microprocessors and/or a systemon an integrated circuit), which are coupled with one or more buses 660.

The energy meter 610 measures the amount of electricity that is flowingon the power line 605 through the charging connection 620. While in oneembodiment of the invention the energy meter 610 measures current flow,in an alternative embodiment of the invention the energy meter 610measures power draw. The energy meter 610 may be an induction coil orother devices suitable for measuring electricity. The energy meter 610may be used to take power samples, as previously described.

The RFID reader 640 reads RFID tags from RFID enabled devices (e.g.,smartcards, key fobs, contactless credit cards, etc.), embedded withRFID tag(s) of operators that want to use the charging station 600. Forexample, in some embodiments a vehicle operator can wave/swipe an RFIDenabled device near the RFID reader 630 to request a charging sessionwith the charging station 600. It should be understood, however, thatcharging sessions may be requested in different ways and accessidentifiers may be presented to the charging station in different ways.For example, in some embodiments the electric vehicles communicate anaccess identifier (e.g., their VIN) to the charging station through aprotocol (e.g., PLC). In such embodiments, the electric vehicle operatormay not be required to present an access identifier (such as the RFIDenabled device) to gain access to the charging station.

The transceiver(s) 635 transmit and receive messages. For example, thetransceiver(s) 635 transmit authorization requests to the server,receive authorization replies from the server, transmit charging sessiondata to the server, etc. The transceiver(s) 635 may also receive powerlimit messages as described herein.

The display unit 645 is used to display messages to vehicle operatorsincluding the price(s) for charging service, current cost for chargingservice, charging status, confirmation messages, error messages,notification messages, etc. The display unit 645 may also displayparking information if the charging station 600 is also acting as aparking meter (e.g., amount of time remaining in minutes, parkingviolation, etc.).

The user interface 640 (which is optional) allows users to interact withthe charging station 600. By way of example, the user interface 650allows electric vehicle operators to request charging sessions, pay forcharging sessions, enter in account and/or payment information, etc.

The processing system 655 may retrieve instruction(s) from the volatilememory 325 and/or the nonvolatile memory 630, and execute theinstructions to perform operations as described above.

As described herein, instructions may refer to specific configurationsof hardware such as application specific integrated circuits (ASICs)configured to perform certain operations or having a predeterminedfunctionality or software instructions stored in memory embodied in anon-transitory computer readable medium. Thus, the techniques shown inthe figures can be implemented using code and data stored and executedon one or more electronic devices (e.g., a server, a charging station,etc.). Such electronic devices store and communicate (internally and/orwith other electronic devices over a network) code and data usingcomputer-readable media, such as non-transitory computer-readablestorage media (e.g., magnetic disks; optical disks; random accessmemory; read only memory; flash memory devices; phase-change memory) andtransitory computer-readable communication media (e.g., electrical,optical, acoustical or other form of propagated signals—such as carrierwaves, infrared signals, digital signals). In addition, such electronicdevices typically include a set of one or more processors coupled to oneor more other components, such as one or more storage devices(non-transitory computer-readable storage media), user input/outputdevices (e.g., a keyboard, a touchscreen, and/or a display), and networkconnections. The coupling of the set of processors and other componentsis typically through one or more busses and bridges (also termed as buscontrollers). Thus, the storage device of a given electronic devicetypically stores code and/or data for execution on the set of one ormore processors of that electronic device. Of course, one or more partsof an embodiment of the invention may be implemented using differentcombinations of software, firmware, and/or hardware.

While the flow diagrams in the figures show a particular order ofoperations performed by certain embodiments of the invention, it shouldbe understood that such order is exemplary (e.g., alternativeembodiments may perform the operations in a different order, combinecertain operations, overlap certain operations, etc.).

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, can be practiced with modificationand alteration within the spirit and scope of the appended claims. Thedescription is thus to be regarded as illustrative instead of limiting.

What is claimed is:
 1. A method for an electric vehicle charging stationto dynamically respond to power limit messages, wherein the electricvehicle charging station includes a set of one or more charging ports,each of which may connect an electric vehicle to the electric vehiclecharging station for charging service, the method comprising: receivinga message that indicates a request to limit an amount of power to anidentified percentage, wherein the message is applicable to one or moreof the set of charging ports; and for each of the set of charging portsthat the message is applicable, performing the following: based on ahistory of power provided through that charging port over a period oftime, causing the amount of power that is capable of being providedthrough that charging port to be limited according to the identifiedpercentage.
 2. The method of claim 1, wherein the history of powerprovided through the charging port over the period of time is an averageof power samples collected during the period of time, each power samplerepresenting an amount of power.
 3. The method of claim 2, wherein thepower samples are collected by the electric vehicle charging stationprior to receiving the message.
 4. The method of claim 2, wherein thepower samples are collected by an external entity coupled with theelectric vehicle charging station.
 5. The method of claim 1, wherein thehistory of power provided through the charging port over the period oftime is calculated by an entity external to the electric vehiclecharging station, and wherein the electric vehicle charging stationreceives the calculated history of power.
 6. A non-transitorycomputer-readable storage medium that provides instructions that, ifexecuted by a processor, will cause said processor to perform operationscomprising: receiving a message that indicates a request to limit anamount of power to an identified percentage, wherein the message isapplicable to one or more of the set of charging ports; and for each ofthe set of charging ports that the message is applicable, performing thefollowing: based on a history of power provided through that chargingport over a period of time, causing the amount of power that is capableof being provided through that charging port to be limited according tothe identified percentage.
 7. The non-transitory computer-readablestorage medium of claim 6, wherein the history of power provided throughthe charging port over the period of time is an average of power samplescollected during the period of time, each power sample representing anamount of power.
 8. The non-transitory computer-readable storage mediumof claim 7, wherein the power samples are collected by the electricvehicle charging station prior to receiving the message.
 9. Thenon-transitory computer-readable storage medium of claim 7, wherein thepower samples are collected by an external entity coupled with theelectric vehicle charging station.
 10. The non-transitorycomputer-readable storage medium of claim 6, wherein the history ofpower provided through the charging port over the period of time iscalculated by an entity external to the electric vehicle chargingstation, and wherein the electric vehicle charging station receives thecalculated history of power.
 11. An apparatus, comprising: an electricvehicle charging station including: a charging port configured toelectrically connect to an electric vehicle to provide power to chargethat electric vehicle; a power control unit coupled with the chargingport, the power control unit configured to control an amount of powerprovided through the charging port; and a set of one or more chargingstation control modules that are configured to perform the following: inresponse to receipt of a message that indicates a request to limit anamount of power to an identified percentage and based on a history ofpower provided through the charging port over a period of time, causethe power control unit to limit the power provided through the chargingport to the identified percentage.
 12. The apparatus of claim 11,wherein the electric vehicle charging station further includes a powersampling unit that is configured to periodically sample power providedthrough the charging port when charging an electric vehicle is ongoingand prior to receipt of the message.
 13. The apparatus of claim 12,wherein set of charging station control modules calculate the history ofpower based on an average of the power samples.